A conventional compressor is disclosed in JP 2003-214369 A. The compressor includes a cylinder having a cylinder chamber, a shaft having an eccentric part, and a roller piston having a roller part, the eccentric part located in the cylinder chamber, the roller part fitted on the eccentric part. The roller part revolves in the cylinder chamber and refrigerant in the cylinder chamber is thereby compressed.
An inner circumferential surface of the cylinder chamber is formed in a noncircular shape with a plurality of curvatures in section, and a radial clearance (which will be referred to as “CP clearance” hereinbelow) between an outer circumferential surface of the roller part and the inner circumferential surface of the cylinder chamber during operation is made so small that reduction in leakage loss of the refrigerant and efficiency improvement are attained.